Die casting apparatus



P 1969 c. F; FULGENZI 3,469,621

DIE CASTING APPARATUS Filed Sept. 29, 1966 INVENTOR CRESCENZO F. FULGENZI ATTORNEY,

United States Patent 3,469,621 DIE CASTING APPARATUS Crescenzo F. Fulgenzi, Parma, Ohio, assignor to Union Carbide Corporation, a corporation of New York Filed Sept. 29, 1966, Ser. No. 582,848 Int. Cl. B22d 17/04; B67d 5/46 US. Cl. 164-316 4 Claims ABSTRACT OF THE DISCLOSURE The subject application concerns a novel shot cylindergooseneck assembly wherein the shot cylinder is positioned within a hollow gooseneck in such a manner as to define a void between the inner wall of the gooseneck and the outer wall of the shot cylinder so that as a piston is forced into the shot cylinder the fluid pressure generated by the molten metal in the assembly is exerted equally on both the inner and outer walls of the shot cylinder which does not contain the advancing piston.

This invention relates to an improved apparatus for die casting high melting point metals. More particularly, it concerns an improved shot cylinder-gooseneck assembly for use in conjunction with a conventional die casting apparatus.

The die casting art is replete with apparatus for die casting low melting point metals such as lead, tin, and zinc. However, it discloses a limited number of apparatus which are suitable for die casting high melting point metals such as aluminum and magnesium.

In co-pending application Ser. No. 320,693, now US. Patent 3,319,702, assigned to the same assignee as the present invention, there is described a novel apparatus for efliciently and economically die casting such high melting point metals. Briefly, the die casting apparatus described therein comprises a pot containing molten metal to be cast, a substantially U-shaped gooseneck having an internal passageway therethrough suspended in the pot, a die cavity communicating with one end of the goosenecks internal passageway, a shot cylinder mounted at the opposite end of the gooseneck and a piston positioned in the shot cylinder which when advanced forces the molten metal from the shot cylinder through the passageway in the gooseneck into the die cavity.

The major problem experienced in designing and fabricating the foregoing type of high temperature die casting apparatus is that those parts of the apparatus which come into contact with the molten metal must be constructed of materials which are resistant to the erosive and corrosive action of the metal being cast.

It is well known that the borides, carbides, and nitrides of the refractory metals are essentially chemically immune to the action of molten metals such as aluminum and the like. However, it is equally well known that these materials possess certain inherent physical limitations which often limit or prohibit their use as mateirals of construction in the fabrication of apparatus for die casting aluminum and other like high melting point metals or alloys.

For example, it is well known that titanium diboride can be formed into almost any intricate shape or pattern but that the resultant article is somewhat brittle. Accordingly, when using a brittle material like titanium diboride as a material of construction, care must be taken to avoid impressing any undue bending or tensile stresses upon that part of the die casting apparatus which is fabricated from such a material. In addition, at high temperatures it is impractical to reinforce a refractory material, such as titanium diboride, with a metal support as their different thermal expansion characteristics will cause the reice fractory material to experience excessive tensile stresses and crack or completely fracture.

Accordingly, it is the principal object of this invention to provide an improved apparatus suitable for die casting high melting point metals such as aluminum and the like.

Another object of the invention is to provide a die casting apparatus of such a design that brittle refractory materials can be advantageously employed as materials of construction.

A further object of the invention is to provide a die casting appartus of such a design that refractory metal borides, carbides and nitrides can be advantageously employed as materials of construction.

A still further object of the invention is to provide an improved shot cylindengooseneck assembly for use in conjunction with a conventional die casting apparatus.

Other objects of the invention will become apparent from a reading of the following specification and claims taken in conjunction with the drawings wherein:

FIGURE 1 is a side elevational view partly in section of a conventional die casting apparatus embodying the invention.

FIGURE 2 is a somewhat enlarged cross-sectional view of the shot cylinder-gooseneck assembly of the invention taken along line 22 of FIGURE 1.

Briefly, the die casting apparatus by means of which the objects of the invention are accomplished comprises a novel shot cylinder-gooseneck assembly wherein the shot cylinder is positioned within a hollow gooseneck in such a manner as to define a void between the inner wall of the gooseneck and the outer Wall of the shot cylinder so that as a piston is forced into the shot cylinder the fluid pressure generated by the molten metal in the assembly is exerted equally on both the inner and outer walls of that portion of the shot cylinder which does not contain the advancing piston, thereby maintaining the remaining unsupported portion of the shot cylinder in an essentially stress free condition.

With reference to the drawings, as shown in FIGURE 1, a die casting apparatus, in general, consists of a holding furnace 10 which supports and maintains a melting basin or pot 12 which, in turn, contains the molten metal to be cast designated as 13. A gooseneck 14 is suspended within the pot 12 and communicates at one of its ends with a die cavity 16. The die cavity is conventional in design and will not be shown in detail. The inner wall of the opposite end of gooseneck 14 is provided with a circumferential protrusion 18 which is adapted to receive and hold the shot cylinder 20. A pump assembly is positioned inside the gooseneck 14 and on top of the shot cylinder 20. The pump assembly comprises a housing 22 which is disposed inside the upper portion of the gooseneck 14 and a piston 24 adapted to engage the bore 21 of the shot cylinder 20. The means for actuating the piston are well known in the art and will not be described.

Referring to FIGURE 2, there is shown, in crosssection, a somewhat enlarged view of the shot cylindergooseneck assembly of the invention. This assembly comprises a substantially U-shaped, hollow gooseneck which communicates at one end with a die cavity (not shown). The other end of the hollow gooseneck 14 is provided on the upper portion of its inner wall with a circumferential protrusion 18 which is suitably notched at 19 to receive and hold the shot cylinder 20. The shot cylinder 20 being provided near its upper end with an outwardly extending flange 23 for engaging the gooseneck 14. The lower portion of the shot cylinder 20 extends into the upper portion of the hollow gooseneck 14 so that their respective outer and inner walls define an annular void or chamber therebetween. The piston 24 communicates with the bore 21 of shot cylinder 20 and is provided with a fill port 25 for allowing the molten metal to fill the shot cylinder-gooseneck assembly without requiring that the piston be completely withdrawn from the shot cylinder.

In actual operation, the shot cylinder-gooseneck assembly is positioned in the molten metal bath below the liquid level and gravity filled by withdrawing the piston from the shot cylinder so as to expose at least the fill port. Once the shot cylinder-gooseneck assembly is suitably filled with molten metal, the piston is forced into the shot cylinder to commence the movement of the molten metal toward the die cavity. As the piston continues its downward movement into the shot cylinder, an increasing fluid pressure is exerted on the shot cylinder. However, as molten metal also occupies the void between the outer wall of the shot cylinder and the inner wall of the gooseneck, such pressure is exerted equally on both the inner and outer walls of that portion of the shot cylinder which does not contain the advancing piston so that the remaining shot cylinder itself experiences no bending or tensile forces which might cause it to rupture or burst. The stroke of the piston is then completed to produce the desired casting. The foregoing procedure is repeated as often as is desired.

An apparatus as described in FIGURE 1 equipped with a titanium diboride shot cylinder was employed to produce 1 /2 pound castings of aluminum at a rate of 5 castings per minute. Forty-two thousand castings were manufactured in this run. Essentially all castings were of excellent quality. Subsequent inspection of the shot cylinder showed that it was in excellent condition and evidenced no cracking or measurable wear. In the main, this was due to the fact that the shot cylinder experienced no bending or tensile stresses during the die casting operation.

At this point, it should be noted that in the present invention the shot cylinder is preferably composed of a hard, dense, refractory material which is resistant to high melting point die casting metals such as aluminum and the like. Some of the materials suitable for the shot cylinder are the borides, carbides, and nitrides of the elements in Groups IV-B, V-B, and VI-B of the Periodic Table (as found on pages 448 and 449 of the 40th edition of the Handbook of Chemistry and Physics), aluminum oxide, and carbon bodies coated with silicon carbide. Titanium diboride is preferred due to its outstanding refractory characteristics although other materials not afiected by the molten metal being cast may also be employed.

It should be apparent from the foregoing that many modifications and changes in the construction and arrangement of the component parts of the apparatus of the invention may be made without departing from the spirit and scope of the invention. For example, the protrusion on the inner wall of the gooseneck need not be circumferential. It may be disposed radially or in any other manner which is suflicient to support the shot cylinder. Likewise, the outwardly extending flange on the shot cylinder need not be complementary circumferential but only sufificient to engage the protrusion. In fact, the recited way of mounting the shot cylinder within the gooseneck is not controlling. Any other means of mounting the shot cylinder within the gooseneck is adequate provided that a void is formed between the inner wall of the gooseneck and the outer wall of the shot cylinder. However, it is to be noted that the void so created must be at least of a sufiicient size to allow molten metal to fill it by capillary action. In actual practice it has been found desirable that the void between the outer wall of the shot cylinder and the inner wall of the gooseneck be at least .05 inch wide.

It will be appreciated by those skilled in the art that the instant invention provides a superior apparatus for die casting high melting point metals due to the fact that it permits brittle, refractory materials to be employed as materials of construction.

What is claimed is:

1. A shot cylinder-gooseneck assembly for use in a piston actuated apparatus for die casting a molten metal into a die cavity comprising:

(a) a substantially U-shaped gooseneck having a continuous opening therethrough, said gooseneck communicating at one of its ends with said die cavity and having a protrusion extending from the inner surface of said gooseneck in close proximity to the other end of said gooseneck;

(b) a hollow shot cylinder engaging said protrusion and extending below said protrusion into the opening in said gooseneck without contacting the inner surface of said gooseneck so as to define a void of at least 0.05 inch between the inner surface of said gooseneck and the outer surface of said hollow shot cylinder, whereby the fluid pressure generated in said shot cylinder-gooseneck assembly as said actuating piston is advanced into said shot cylinder is exerted equally on the inner and outer walls of that portion of the shot cylinder which does not contain said actuating piston so as to maintain said shot cylinder in an essentially stress free condition.

2. The shot cylindergooseneck assembly of claim 1 wherein said protrusion in said gooseneck is provided with a notch for receiving said shot cylinder; and said shot cylinder is provided at its upper end with a flange for engaging said notched protrusion in said gooseneck.

3. The shot cylinder-gooseneck assembly of claim 1 wherein the shot cylinder is composed of a refractory material.

4. The shot cylinder-gooseneck assembly of claim 1 wherein the shot cylinder is composed of titanium diboride.

References Cited UNITED STATES PATENTS 2,145,553 1/1939 Morin 103-153 2,390,263 12/ 1945 Mills 164-316 3,209,418 10/1965 Smith 164-318 3,3 15,651 4/1967 Dangauthier 92--l7l X 3,319,702 5/1967 Hartwig et al. 164--316 J. SPENCER OVERHOLSER, Primary Examiner R. SPENCER ANNEAR, Assistant Examiner US. Cl. X.R. 

